1. Field of the Invention
The present invention relates to natural language understanding systems, and more particularly to a method and system for non-intrusively verifying a user based on behavior of the user.
2. Description of the Related Art
Traditional methods for speaker verification (or identification) rely on specific inputs from the user for the sole purpose of the verification. These methods may include providing speech samples and answering biometric questions. Once verified, the speaker is permitted to access the target system, and typically no further verification is performed. Even if additional verification is performed, it requires more specific inputs from the user for the purpose of verification. This is intrusive to the user.
Prior art speaker verification systems (or user verification systems, for systems without a spoken input modality) validate the identity of a given user on the basis of one or more of the following criteria:
1. Who the user is, which may be determined by the user""s voice, fingerprint, handwriting, etc.
2. What the user knows, which may be determined by a password, or answers to some biometric questions (e.g., what is the mother""s maiden name?), etc.
3. What the user possesses, such as an identification document, a key, a cellular phone with a particular number, etc.
All of the above methods for verification may be defeated if an imposter knows or possesses the information, such as the key or a maiden name, etc.
Therefore, a need exists for a method and system for determining an identity of a user based on the users behavior. A further need exists for a non-intrusive user verification system.
A system for verifying user identity, in accordance with the present invention, includes a conversational system for receiving inputs from a user and transforming the inputs into formal commands. A behavior verifier is coupled to the conversational system for extracting features from the inputs. The features include behavior patterns of the user.
The behavior verifier is adapted to compare the input behavior to a behavior model to determine if the user is authorized to interact with the system.
In alternate embodiments, the conversational system may include a natural language understanding unit for interpreting speech received as the inputs. The inputs may include at least one of speech, handwriting, text, and gestures. The behavior verifier may include a feature extractor for extracting feature vectors from the inputs.
The feature vectors may include at least one of language model scores, acoustic model scores, natural language and understanding scores, command predication scores and/or pronunciation scores. The feature vectors may include at least one of information about system responses to the user, duration between user commands and a dialog state between the user and the system, and/or types of input modalities employed by the user. The behavior model may include a plurality of models. The behavior verifier may include a probability calculator. The probability calculator may be adapted to calculate a first probability that the user is authorized to interact with the system based on the user""s behavior. The behavior verifier may include a model constructor for constructing the behavior model for a user, the behavior model being employed by the probability calculator to compare behavior to current behavior of the user. The system may further include an acoustic and biometric verifier for determining acoustic and biometric information from the user and determining a second probability that the user is authorized to interact with the system based on the user""s acoustic or biometric information, and the behavior verifier may include a probability mixer adapted for integrating the first probability with the second probability to verify that the user is authorized to interact with the system. The first probability may be compared to a threshold probability to determine if the user is authorized to use the system.
A method for verifying a user based on behavior, in accordance with the present invention, includes the steps of providing inputs to a conversational system for receiving the inputs from a user and transforming the inputs into formal commands, extracting features from the inputs, the features including behavior patterns of the user, and comparing the input behavior to a behavior model to determine if the user is authorized to interact with the system.
In other methods, the conversational system may include a natural language understanding unit, and the method may further include the step of interpreting speech received as the inputs. The inputs may include at least one of speech, handwriting, text, and gestures. The feature vectors may include at least one of language model scores, acoustic model scores, natural language and understanding scores, command predication scores and/or pronunciation scores. The feature vectors may include at least one of information about system responses to the user, duration between user commands and a dialog state between the user and the system, and/or types of input modalities employed by the user. The behavior verifier may include a probability calculator, and the method may include the step of calculating a first probability on the probability calculator, the first probability for indicating whether the user is authorized to interact with the system based on the user""s behavior.
In still other methods, the behavior verifier may include a model constructor, and the method may include the step of constructing the behavior model for a user, the behavior model being employed by the probability calculator to compare behavior to current behavior of the user. An acoustic and biometric verifier may be included for determining acoustic and biometric information from the user, and the method further include the steps of determining a second probability for indicating whether the user is authorized to interact with the system based on the user""s acoustic or biometric information and integrating the first probability with the second probability, by employing a probability mixer, to verify that the user is authorized to interact with the system. The first probability may be compared to a threshold probability to determine if the user is authorized to use the system. The methods and method steps of the present invention may be implemented by a program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform the method steps for verifying a user based on behavior.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.